Forstall's name is on 166 pending patent applications. That's
more than anyone at the company, according to data from
investment bank MDB Capital.

"He's one of, if not the most prolific inventors at Apple," says
Erin-Michael Gill, Managing Director and Chief Intellectual
Property Office at MDB. "If this guy is who the data seems to
imply he is, letting him leave is a huge deal."

MDB specializes in analyzing patent filings. It has its own
database of patent information. Gill sent us a table of Apple
patents filings by employees. Gill warns that it's difficult to
be completely accurate about pending patents, but MDB's data is
the "best data available publicly."

The two people that are filling his role combined have less than
half as many patents pending. Craig Federighi, who will lead OSX
and iOS, has 16 patents pending. Jony Ive, who will lead
interface design, has 51 pending.

It's important to note there's a key difference between patents
from Ive, and Forstall. Ive's patents are design patents, which
cover the look and feel of Apple's products. Forstall's are
product patents that are at the core of how iOS works, according
to Gill.

For instance, Forstall's name is second on the patent that lays
out exactly how the iPhone and iPad work. The first name on that patent is
Steve Jobs, Apple's late cofounder, who
died last year. Now, Apple will have to carry on without either
of them.

Forstall was
a divisive character inside Apple. When he left, there was a
spin that it was good for Apple because it was getting rid of a
jerky manager. However, Forstall also had a lot of people who
were loyal to him at Apple. And if some of the people he
collaborated with decide to leave with him, Gill warns Apple
could easily lose 5-6 of its most important inventors.